Currently, ophthalmic lenses are often made by cast molding, in which a reactive monomer material is deposited in a cavity defined between optical surfaces of opposing mold parts. To prepare a lens using such mold parts, an uncured hydrogel lens formulation is placed between a plastic disposable front curve mold part and a plastic disposable back curve mold part.
The front curve mold part and the back curve mold part are typically formed via injection molding techniques wherein melted plastic is forced into highly machined steel tooling with at least one surface of optical quality.
The front curve and back curve mold parts are brought together to shape the Lens according to desired lens parameters. The lens formulation is subsequently cured, for example by exposure to heat and light, thereby forming a lens. Following cure, the mold parts are separated and the lens is removed from the mold parts for hydration and packaging. However, the nature of cast molding processes and equipment make it difficult to form custom lenses specific to a particular patient's eye or a particular application.
Consequently, in prior descriptions by the same inventive entity, methods and apparatus for forming customized lenses via the use of free-form techniques have been described. An important aspect of these novel techniques is that a lens is produced in a free-form manner, that is where one of two lens surfaces is formed in a free-formed manner without the need of using cast molding, lathing, or other tooling.
A free-formed surface and base may include fluent lens s reactive media included in the free-formed surface at some point during the formation. This combination results in a device sometimes referred to as a lens precursor. Fixing radiation and hydration treatments may typically be utilized to convert a lens precursor into an ophthalmic lens.
Some of the free-formed lenses created in this manner may need different methods and/or structural features for the control of all or some of the fluent lens reactive media included in the lens precursor. By controlling some of all of the fluent lens reactive media, physical and/or optical parameters of a lens design may be produced. The new methods and features are the subject matter of the present invention.